1. Field of the Invention:
This invention relates in general to oil well workover operations and, in particular, to the insertion of coiled tubing into a drill string.
2. Description of the Prior Art:
In some types of oil well workover operations, coiled tubing is run into the tubing string or drill string of the oil well. For example, coiled tubing may be used to inject nitrogen into a well in order to test the productivity of a particular zone. When coiled tubing is being inserted into a well, pressure control equipment, such as a blowout preventor stack, is used to prevent a blowout. In the prior art, the pressure control equipment was connected to the drill string by flanging a threaded sub onto the bottom of the pressure control equipment, and then threading the sub into the upper end of the drill string. Such a method required hanging the pressure control equipment from a crane while stabbing and rotating to make up the connection. The operation can be particularly difficult on a floating vessel, due to the relative motion between the crane and the well head. In rough seas, such a connection has been known to take as much as two or three hours to complete.
The apparatus of this invention utilizes a coupling which is an adaption of the quick connect fitting shown in U.S. Pat. No. 3,134,613 (Regan). The Regan coupling was used to connect a shutoff valve to the tubing string of an oil well to prevent a blowout. The coupling allowed the shutoff to be merely slipped over and latched onto the upper end of the tubing string to shut off the fluid flow. The coupling had a tubular housing and a plurality of circumferentially spaced latch elements within the housing. The latch elements were pivotable between inner, extended positions, wherein the latch elements engaged the drill string, and outer, retracted positions. The latch elements had inner cam surfaces engageable with the upper end of the tubing string to pivot the latch elements outwardly into the retracted position as the housing was slipped over the upper end of the tubing string. The coupling also had manual retracting means for pivoting the latch elements into the retracted positions, to cause the latch elements to disengage the tubing string when it was desired to remove the housing from the upper end of the tubing string. The release means of the Regan quick connect fitting was not remotely operable, and the latch elements were not designed to support the entire weight of the tubing string.
It is preferable that an apparatus for inserting coiled tubing into a drill string be remotely releasable. The release means should be remotely operable, because the coupling will be positioned high above the deck of the floating vessel to allow for wave and tidal action. Also, there are times when it is desirable to support the weight of the tubing string with the coupling, so the latch elements or dogs should be designed to support such weight.